The major revamp of the Scottish National Gallery (SNG) has received a £5m boost of national lottery funds.

The £16.8m extension of the gallery will improve, update and better display the gallery's collection of Scottish art.

The new displays will at last do them "justice", the director of the gallery said.

The Heritage Lottery Fund have now confirmed a £4.94m award to the scheme.

Preparation is due to begin in September 2016, with construction work commencing on site in January 2017 and continuing until summer 2018.

The new space will be open to the public in autumn of 2018.

The planned redevelopment of the SNG, entitled Celebrating Scotland’s Art, will triple the exhibition space available to the Scottish collection from 440 m to 1320 m, and improve visitor access and circulation throughout the SNG complex.

When the currant director general of the National Galleries, Sir John Leighton, joined the institution in 2006, he said the display of Scottish art in the windowless concrete basement resembled an "apology" and he was "deeply unhappy" about it.

"One of the enduring weaknesses in recent times has been the display of the historic Scottish collection," he later said.

The gallery is home to a collection of masterpieces of Scottish art, including work by Allan Ramsay, Sir Henry Raeburn and Sir David Wilkie, as well as many others.

The new displays will tell the story of Scottish art from the 17th to the mid-20th century, including the Scottish Colourists.

The project, the galleries say, will mark a "fundamental change in the way the Gallery presents historical Scottish art."

The design will open up a suite of new gallery spaces which, for the first time, will be directly accessible from East Princes St Gardens.

The space will have natural light, and will have views into the Gardens and the city beyond.

The terrace outside the gallery will be expanded and a new pathway created.

Access to the gardens will be improved - these plans are currently with City of Edinburgh Council for consideration.

In January of this year, the National Galleries of Scotland Bill was passed by the Scottish Parliament to allow the transfer of a narrow strip of common good land in East Princes St Gardens to the NGS.

This land is a steep, grassy bank between the pedestrian walkway and the windows of the Gallery’s office accommodation.

The galleries say this will "create a new elevation which aligns with that of the existing visitor facilities at Gardens level.

"As well as contributing to the increase in exhibition space within the Gallery it will also create a wider footpath at the level above, which is a busy and often congested pedestrian thoroughfare," the NGS said in a statement.

During the renovation, the SNG will remain open to the public with access to the main floor rooms.

Michael Clarke, director of the Scottish National Gallery and the project’s director, said: "We are absolutely delighted that the Project has received the full and generous support of the Heritage Lottery Fund.

"Scotland’s historic art will at last be displayed in a space that will do it justice and enable our visitors from home and abroad to appreciate fully its many and distinctive qualities.

"Our world-famous collections, displayed in our historic and sympathetically remodelled gallery, will reinforce our position as one of Scotland’s ‘must see’ attractions."

Lucy Casot, head of the Heritage Lottery Fund in Scotland, said: “We are delighted that thanks to the National Lottery playing public, the most important collection of Scottish Art in the world will have a home worthy of its impressive heritage.

"This project will breathe new life into the collection so that it can bring joy and inspiration to national and international visitors. Importantly, it will also reach out to schools and community groups across the country so that they too can learn from and enjoy these national treasures."

Hoskins Architects are designing the revamp of the gallery.

Before his death earlier this year, the firm’s founder, Gareth Hoskins OBE, created a design for the project, which is being taken forward by director Chris Coleman-Smith.